1. Field of the Invention
This invention relates to acoustic arrays and, in particular, to endfire microphone or loudspeaker arrays.
2. Description of the Prior Art
It has been desirable to secure improved response for a wide range of frequencies, such as is encountered in the transmission of speech or music. One apparatus used for achieving this objective was through the use of an impedance device comprising a plurality of substantially equal diameter tubes having uniformly varying lengths arranged in a bundle. Another apparatus used a single tube with apertures spaced equally apart having substantially the same dimensions. Typically, such impedance devices are coupled to a microphone or a loudspeaker and are known as endfire acoustic arrays.
In each of the devices described above, the response pattern comprises one main lobe and a plurality of gradually decreasing smaller sidelobes. These sidelobes represent undesired response to signals coming from other than a desired direction.